Vanadocene

Structural formula
Staggered conformation
General
Surname	Vanadocene
other names	Bis (η 5 -cyclopentadienyl) vanadium Di (cyclopentadienyl) vanadium (Cp) 2 V, VCp 2
Molecular formula	C 10 H 10 V
Brief description	purple solid
External identifiers / databases
CAS number 1277-47-0 EC number 620-850-1 ECHA InfoCard 100.149.756 PubChem 11984630 Wikidata Q305472
properties
Molar mass	181.128 g mol −1
Physical state	firmly
Melting point	167 ° C
solubility	decomposes in water
safety instructions
GHS labeling of hazardous substances danger H and P phrases H: 228-301-311-315-319-331-335 P: 210-261-280-301 + 310-305 + 351 + 338-311
As far as possible and customary, SI units are used. Unless otherwise noted, the data given apply to standard conditions .

Vanadocene , or bis (cyclopentadienyl) vanadium, abbreviated VCp ₂ is an organometallic compound from the family of metallocenes . It forms a sandwich complex analogous to ferrocene , but does not follow the 18-electron rule , as it has only 15 valence electrons .

presentation

Vanadocene was first made in 1954 by Birmingham, Fischer and Wilkinson by reducing vanadocene dichloride with aluminum hydride . The vanadocene was then sublimed at 100 ° C.

In 1977 Köhler et al. the production of vanadocene by reacting the vanadium complex [V ₂ Cl ₃ (THF) ₆ ] ₂ [Zn ₂ Cl ₆ ] with cyclopentadienyl sodium :

${\displaystyle \mathrm {4\ VCl_{3}+12\ THF\ \rightarrow \ 4\ [VCl_{3}\ 3\ THF]{\xrightarrow[{}]{2\ Zn}}\ [V_{2}Cl_{3}(THF)_{6}]_{2}[Zn_{2}Cl_{6}]\ } }$

${\displaystyle \mathrm {[V_{2}Cl_{3}(THF)_{6}]_{2}[Zn_{2}Cl_{6}]\ +\ 8\ Na(C_{5}H_{5})\ \rightarrow \ 4\ V(C_{5}H_{5})_{2}} }$

If vanadium (III) chloride is reacted directly with cyclopentadienyl sodium, the latter acts as a reducing agent and dihydrofulvalene is formed as a by-product through the coupling of two Cp residues :

${\displaystyle \mathrm {2\ VCl_{3}\ +\ 6\ Na(C_{5}H_{5})\ \rightarrow \ 2\ V(C_{5}H_{5})_{2}\ +\ 6\ NaCl\ +\ H_{5}C_{5}-C_{5}H_{5}} }$

Vanadocene conformers with D _5d (left) and D _5h symmetry (right)

properties

Vanadocene is a purple colored, crystalline, paramagnetic solid. In the solid state, the molecules D have _5d symmetry . The vanadium (II) ion lies equidistant between the two cyclopentadienyl rings in the center of symmetry. The average V – C bond length is 226  pm and the distance between the rings is 390 pm. The cyclopentadienyl rings in vanadocene are dynamically disrupted at temperatures above 170  K and are only fully ordered below 108 K. The dissociation energy for the Cp – V bond is given as 145 kJ · mol ⁻¹ or 369 kJ · mol ⁻¹ , depending on the literature .

Reactions

Vanadocene is a reactive molecule. It can easily be oxidized to a monocation by reaction with a ferrocenium salt in toluene:

${\displaystyle \mathrm {V(C_{5}H_{5})_{2}\ +\ [Fe(C_{5}H_{5})_{2}][BR_{4}]\ {\xrightarrow[{Toluol}]{}}\ [V(C_{5}H_{5})_{2}][BR_{4}]+Fe(C_{5}H_{5})_{2}\ } }$

${\displaystyle \mathrm {\ mit\ R=Phenyl\ oder\ 4-Fluorophenyl} }$

Since vanadocene only has 15 valence electrons, it will readily react with other ligands. Vanadocene reacts with acetylene derivatives e.g. B. on the corresponding vanadium cyclopropene complexes:

In the reductive ring exchange with butyllithium in the presence of 1,3-cyclohexadiene , a cyclopentadienyl ring of the vanadocene can be replaced by a benzene ring:

${\displaystyle \mathrm {V(C_{5}H_{5})_{2}\ {\xrightarrow[{C_{6}H_{8}}]{LiC_{4}H_{9}}}\ V(C_{5}H_{5})(C_{6}H_{6})} }$

Individual evidence

1. ↑ ^{a b} Christoph Elschenbroich: Organometallchemie . BG Teubner Verlag, 2008, ISBN 978-3-8351-0167-8 ( page 452 in the Google book search).
2. ^ Electrochemical Society: Proceedings of the Thirteenth International Conference on Chemical Vapor . 1996, ISBN 978-1-56677-155-9 ( page 757 in the google book search).
3. ↑ ^{a b} Data sheet bis (cyclopentadienyl) vanadium (II) from Sigma-Aldrich , accessed on December 8, 2011 ( PDF ).
4. ↑ JM Birmingham, AK Fischer, G. Wilkinson: The Reduction of Bis-cyclopentadienyl Compounds . In: Natural Sciences . 42, No. 4, 1955, p. 96. doi : 10.1007 / BF00617242 .
5. ↑ C. Lorber: "Vanadium Organometallics." Chapter 5.01. Comprehensive Organometallic Chemistry III. Elsevier, 2007. 1-60.
6. ↑ ^{a b} Markus Jordan: Azines in the coordination sphere of vanadocene derivatives with different oxidation states . Oldenburg 2009, DNB  996730079 , urn : nbn: de: gbv: 715-oops-8831 (dissertation, University of Oldenburg).
7. ↑ Integrated synthesis internship (ISP) Uni Hamburg: Vanadocen , (PDF; 58 kB).
8. ↑ Robin D. Rogers, Jerry L. Atwood, Don Foust, Marvin D. Rausch: Crystal Structure of Vanadocene . In: Journal of Crystal and Molecular Structure . 11, No. 5-6, 1981, pp. 183-188. doi : 10.1007 / BF01210393 .
9. ↑ F. Jellinek: The structure of the osmocene. In: Journal of Nature Research B . 14, 1959, pp. 737-738 ( online ).
10. ^ AF Holleman , E. Wiberg , N. Wiberg : Textbook of Inorganic Chemistry . 101st edition. Walter de Gruyter, Berlin 1995, ISBN 3-11-012641-9 , pp. 1699-1703.
11. ↑ James E. Huheey, Ellen A. Keiter, Richard Keiter: Inorganic Chemistry: Principles of Structure and Reactivity . de Gruyter Verlag, 2003, ISBN 3-11-017903-2 ( page 797 in the Google book search).
12. ↑ Fausto Calderazzo, Isabella Ferri, Guido Pampaloni, Ulli Englert: Oxidation Products of Vanadocene and of Its Permethylated Analogue, Including the Isolation and the Reactivity of the Unsolvated [VCp] Cation . In: Organometallics . 18, No. 13, 1999, pp. 2452-2458. doi : 10.1021 / om9809320 .
13. ↑ Thomas Kupfer: Representation and characterization of strained [n] metalloarenophanes and boroles . Würzburg 2007, DNB  986490075 , urn : nbn: de: bvb: 20-opus-24999 (dissertation, University of Würzburg).

literature

• AF Holleman , E. Wiberg , N. Wiberg : Textbook of Inorganic Chemistry . 101st edition. Walter de Gruyter, Berlin 1995, ISBN 3-11-012641-9 , pp. 1699-1703.
• SCRIPTUM for module AC-4 (Sundermeyer) Uni Marburg, pp. 148–151 (PDF; 1.7 MB).